In the mining industry, structural support to maintain a mine is typically attained with various types of mining bolts. These mining bolts can consist of various designs:
1. Mechanical bolts which have a smooth round shaft - a forged head and a bearing plate on one end, and an expansion anchor at the other. (Tensioned Bolt)
2. Fully grouted resin bolts which consist of a reinforcing bar with a forged head and bearing plate on one end. The rest of the reinforcing bar is left as is. These bolts are used with polyester resin cartridges to grout around the bar and fill the annulus between the bore hole and the reinforcing bar. (Untensioned Bolt)
3. Partially anchored tensioned bolt:
A. A partially anchored (polyester resin) reinforcing bar with a frangible delay nut of various design at the bottom end plus a bearing plate. (Tensioned Bolt) Referred to as a "Tension Rebar" Bolt.
B. A partially anchored (polyester resin) reinforcing bar that is threaded at its bottom portion and connected to a smooth bolt on the bottom plus a bearing plate. The reinforcing bar is grouted in polyester resin. The coupling that joins the rebar to the smooth bolt on the bottom has a delay mechanism to permit the resin to be mixed and subsequently allow take up in the coupling after the resin becomes hard. A typical bolt of this design is U.S. Pat. No. 4,477,209 entitled Combo Anchor.RTM.. (Tensioned Bolt)
C. A partially grouted smooth bolt that features a nut on the threaded top end to which is attached a mixing wire to mix the resin. The bottom end has a forged head, dual thrust washers, and a bearing plate. This is a tensioned bolt called the "Fastorq Bolt".TM. patented by Dupont.
4. A grouping of bolts using either a headed reinforcing bar or a headed smooth bar with a bearing plate. At the top end is a mechanical anchor that is reinforced with polyester resin. (Tensioned Bolt) A typical bolt of this design is U.S. Pat. No. 4,655,645 entitled Spiral Bolt.RTM..
5. A smooth headed bolt with a buttress deformation at the top end which screws into a compressible plastic formable material and a bearing plate at the bottom. A polyester resin cartridge can also be used to reinforce this anchorage with the plastic tube. (Tension Bolt) U.S. Pat. No. 4,659,295 called DYNA ROK.TM. Anchors.
6. A long tube of high strength steel, with a slot along its entire length. One end is tapered for insertion into a drilled hole in the roof of the mine. The other end has a welded ring flange to retain a roof plate. This bolt is driven into the hole. (Untensioned Bolt) named Split Set.RTM..
7. A bolt that is manufactured from a steel tube. The tube has been mechanically reshaped to an outer diameter that is smaller. Bushings are pressed onto the ends, which are sealed through welding. The lower bushing is flanged to hold a bearing plate in place. A hole is drilled through the lower bushing and the wall of the tube to allow water to be injected into the bolt. During installation, the high pressure water causes the bolt to expand and forms it to irregularities in the drill hole. After installation, the water pressure is released. (untensioned) Bolt called Swellex.RTM., manufactured by Atlas Copco Co.
8. Screwing a threaded bolt into set resin to attain a tensioned system such as the Clarich.TM. roof bolt.
All of the above bolts require a hole to be drilled into the roof and everything that occurs, as far as anchorage is concerned, is confined within the borehole. Contrary to the above examples, there is a bolt which requires no borehole for installation:
9. A bolt which is driven into the roof of a mine, requiring no borehole, similar to driving a nail into wood. This is called the Pin-Set Bolt.RTM., U.S. Pat. No. 3,643,542; date of issue: Feb. 22, 1972. (Untensioned Bolt).
The present invention is a mining bolt which is directly screwed into the rock and a method with respect to the same. It may or may not be used with any amount of resin, be it a point anchor system or a fully grouted system. The need for delay mechanisms or expansion anchors is then eliminated to establish a bolt under tension in the rock.